Carburetor



Aug. 10, 1937. R. F. BRAcKl-z CARBURETOR Filed Aug. 28, 1935 Patented Aug. l0, 1937 UNITED STATES vPATENT Aol-Ficrl oAnBUnE'roa Robert F. Bracke, Chicago, lll. Application August 2s, 1935, serial No. sazs 1o claims.. (c1. zel-,72)

fuel tank and also varies with the gradient of f the road over which the vehicle is traveling. In fuel lift carburetors heretofore used it has been customary to maintain at all times sufficient suction in the iioat bowl of the carburetor to lift the fuel from the fuel tank to the float bowl through the maximum head which will exist under any conditions of operation of the vehicle. This means that during most of the period of vehicle operation an unnecessarily high suction is maintained in the carburetor oat bowl and this decreases the eiliciency of operation of the carburetor.

An object of my invention is to provide a carburetor wherein the float bowl suction varies with the head through which the fuel mustbe lifted so that the suction in the -oat bowl is suicient only to overcome the head existing at any given time.

- Another object of my invention is to improve the efficiency-of fuel lift carburetors.

Another object is to maintain a constant ratio between the nozzle suction and the oat bowl suction.

Another object is to provide a carburetor which provides greater engine power under most operating conditions. A

Other objects and advantages will become apparent as the description proceeds.

My present invention is an improvement over the subject-matter of my co-pending application, Serial No. 6,421, filed February 14, 1935.

In the' accompanying drawing:

Figure 1 -is a vertical section through a carburetor embodying my invention, the connection between ,the carburetor and the fuel tank being diagrammatically indicated; and y Figure 2 is a sectional vicw of a detail, being taken on the line 2--2 of Figure 1.

Referring to the drawing, I have shown a down draft type of fuel lift carburetor wherein the upperI casting A and the lower casting B are secured together by any suitable means and together compose the main body of the carburetor.

The particular means for securing the castings A and B together are illustrated as bolts i0, and a suitable washer or gasket I2 is clamped between the castings A and B to form an air-tight seal therebetween.

The upper casting A has an air horn I4 which is shown as communicating directly with atmosphere, but which may be connected to a suitable air lter and silencer of the type now commonly used on automobile en- 10 gines. In the air horn I4 is a hub I6 supported by spokes Il. The hub I6 has a vertical opening therethrough in which a Venturi tube or nozzle 20 is suitably aiilxed. The nozzle 2li has a primary air inlet 22 converging toward 15 a throat 24 terminating at a step 26. Immediately beneath the step 26 are the inner ends of diagonal fuel feed passages 28 which establish communication between the interior of the nozzle and an annular chamber 30 surrounding 20 the adjacent'portion of the nozzle.

Part of the air .entering the air horn I4 passes into the inlet 22 of the nozzle and mixes with fuel supplied through the diagonal passages 28. The mixture thus formed flows through the flaring portion 32,01 the nozzle and strikes the flat surface 34 provided by a secondary air valve 36 mounted for reciprocatory movement on the lower end of the nozzle 20; After the mixture strikes the surface 34 it flows radially and thence into the mixing chamber 38.- When the engine is operating at normal speed the secondary air valve 36 is drawn down-below the position shown in the drawing and secondary air ows into the mixing-chambery 38 between the air valve 36 and its cooperating throat 40. From the mixing chamber-36 the combustible mixture flows through suitable passages into the upper end of the throttle bore 42 and thence into the intake manifold 44 to which the carburetor is attached y, by bolts 46.

A throttle valve 46 is located in the throttle bore 42 and is mounted on a pivoted shaft 50 attached to a lever 52 vwhich is connected with the usual accelerator pedal and hand throttle of the automobile. The idle position of the `throttle valve 48 is controlled by an adjusting screw 54 which contacts with a lug 56, and the full throttle position of the valve 48 is similarly determined by the engagement of a stop 56 with the lug 56. 50

My carburetor includes a oat bowl 60 containing a iioat 62 which closes a gravity. opened valve 64 when the float bowl 60 is full of fuel.- 'I'he valve 64 controls communication between the float bowl 60 and the fuel tank 66 which is ordi- 55 narily located at the rear of the vehicle and below the carburetor. The fuel is sucked from the tank 66 by means which will now be described. Part of the air entering the air horn |4 passes 5 into the upper end of a passage 68 and thence through the opening 18 in choke plate 12 and into the chamber 14 formed by a cap 16 attached to the casting B by means of the spring plate 18 and screw 88. From the chamber 14 the air passes through a second opening 82 in the choke plate 12 and into a booster nozzle 84 which discharges into a bore 86. 'I'he bore 86 communicates with the upper end of the throttle bore 42 through an orice 88 Whose effective size is controlled 15 by the tapered metering pin 88 which is movable with the secondary air valve 36. The throat of the booster 84 is connected by way of small passages 82 4and ducts 84 and 86 with the upper end vof the float bowl 68, so that the suction created in the throat of the booster 84 is communicated to the float bowl'and draws thereinto fuel from the main tank 66 when the valve 64 is open.

'Ijhe fuel for the primary nozzle 22 is supplied thereto from the float bowl 68 through an accelerator pump comprising a cylinder V88 in which is located a piston |88. The fuel enters the lower end of the cylinder 88 and passes upwardly through ports |82 in the piston. when the engine is idling the valve |84 is in the position shown in the drawing and the fuel for the engine is supplied through the small port |86 located therein, but when the engine requires more fuel this valve |84 is raised from its seat and additional fuel flows around the outside edge of this valve.

The fuel flowing past the valve |84 passes upwardly through an orifice |88 whose eifective area is controlled by a pin ||8 carried by the piston |88. The portion of the pin ||8 which is located .min the orifice |88 is gradually tapered from one end to the other, so that when the piston is in the lower position shown in the drawing, the orice |88 contains a maximum restriction and the effective area of this oriiice gradually increases as the piston |88 is raised. The fuel passing through the orifice |88 reaches the diagonal passages 28 and annular chamber 38 by way of the bore I|2.

The piston |88 is raised by a piston rod ||4 resting upon an adjustable screw ||6 carried by one arm of a lever ||8 which is pivoted to the casting B at |28. The other arm of the lever ||8 is connected to the throttle controllever 62 by a link |22, so that as the throttle valve 48 is opened the piston |88 is raised.

When the throttle valve 48 is suddently opened through a wide range of movement, the additional quantity of fuel supplied to the nozzle 28 by the piston |88 would be too great if means were not `provided for permitting some of the fuel above this piston to bypass the piston and flow back into the float bowl of the carburetor. Accordingly, I provide a second series of passages |24 in the piston 88, these passages being normally closed by a spring pressed valve |26 so that when the piston is suddenly moved upward through a long stroke, part of the fuel ahead of the piston can flow through the passages |24 and past the valve |26 and thence back to the float bowl 68. The piston |88 merely rests upon the upper end of the rod ||4 and is returned by a spring |28. l It is important that no air leak into the float bowl 68 around the piston rod. |4. Accordingly, I-provide an annular space |38 intermediate the guide for this piston rod and connect this space by way of a'duct |32 with that part of the throttle bore which is below the throttle valve 48, so that any air seeping along the piston rod ||4 will be drawn into the intake manifold and will not reach the float bowl of the carburetor. It is to be understood that the screw ||6 may be adjusted to regulate the idle position of the metering pin III.

My invention particularly relates to the method of controlling the suction existing in the float bowl of the carburetor. 'I'his suction is created by the booster-84 and I control the degree of suction created by this booster by means of the pin 88 associated with the secondary air valve 436. The positions of the secondary air valve 36 and control pin 88 are in turn regulated by the suction createdin a chamber |84 formed therebeneath by the downwardly extending cup |36 of the air valve casting and the upwardly extending guide |38.

The secondary air valve 36 and control pin 88 are urgedupwardly by a spring |48 which exerts its force upon a plate |42 located beneath the enlarged head of the control pin 88. The secondary air valve and control pin are drawn downwardly against the tension of this spring by the suction created in the chamber |84 through the orifice |44 and passage |46 (Figure 2) which connect this chamber with the upper end of the throttle bore 42. The suction in the upper end of the throttle bore 42 is dependent upon the position of the throttle valve 48 and the conditions under which the engine is operating.

I provide special means for varying the degree of suction in the chamber |34 independently of the suction existing in the upper end of the throttle bore 42. According to my invention the de`- gree of suction existing in the chamber |34 is varied in accordance with the variations in head through which the fuel must be lifted from the tank 66 to the float bowl 68 of the carburetor. This means that the positions of the secondary air valve 36 and of the control pin 88 are similarly varied with the variations of the fuel lift head, so that the suction maintained in the float bowl by the booster 84 likewise varies with this head.

Fuel from the main tank 66 is drawn to the carburetor through a pipe |48 which connects with a chamber |58 formed in a part of the casting B. One side of the chamber |58 is closed by a flexible diaphragm |52 which is secured in place by a cap |54 which is bolted or otherwise suitably attached to the casting B. The diaphragm |52 may be made of any suitable material but is preferably composed of the same material which is used in the fuel pumps now commonly associated with automobile engines for supplying fuel thereto. The upper end of the chamber |58 connects with the float bowl inlet valve 64 by way of bores |56 and |58.

The diaphragm |52 is urged to the left by a spring |68 which is confined between one wall of the chamber |58 and a metal cup |62 which rests against the diaphragm |52. The diaphragm is moved to the right in opposition to the spring |68 by the suction created in the chamber |88 to overcome the difference in elevation between Athe inlet valve 64 and the upper surface of the with the fuel lift head and controls a metering pin |64 which is lightly pressed against the lefthand side of the diaphragm by a spring |66 resting upon a sleeve |68 adjustably secured. as, for example, bypthreads in the cap |54. 'I'he pin |64 has a reduced and tapered left-hand end which variably controls an orice which connects atmosphere with a pipe |12 communicating through ducts |14 and |16 with the chamber |34 10 located beneath the secondary air valve.

When the fuel tank 66 is full and the automobile is traveling down' hill, little suction is rev quired to lift fuel from the tank 66' to the oat bowl of the carburetor. Under these conditions l5 only a small amount of suction is maintained in the chamber |50 and the metering pin |64 almost closes the orifice |10, so that the suction maintained in the chamber |34 beneath the secondary air valve is approximately equal to the suction existing in the upper end of the throttle bore 42. The secondary air valve 36 and metering pin 90 are accordingly drawn downwardly against the tension of the spring |40 and the outlet of the booster 84 is restricted so that it creates only a small amount of suction in the float bowl 60. On the other hand, when the fuel tank 66 is nearly empty and the vehicle is traveling up hill, maximum suction is required in the oatbowl 60 to draw fuel from the tank 66. Under these conditions maximum suction is maintained in the chamber |50 and the diaphragm |52 is drawn inwardly against the spring |60. The light spring |66 moves the metering pin |64 to the right and allows air to enter through the orice |10 and flow into the chamber |34 beneath the secondary air valve which assumes a higer position, thereby maintaining a greater suction in mixing chamber 38 and in the upper end of throttle bore 42. 'This greater suction causes booster 84 to create maximum suction in float bowl 60 and also increases the fuel lifting capacity of nozzle 20. y y It is not to be understood that the degree o suction existing in the float bowl 60 alternates rapidly between the m-aximum and Under ordinary operating conditions the suction in this oat bowl changes slowly as the fuel in the tank 66 is consumed and changes more rapidly with changes in the gradient of the road over which the vehicle is traveling. The parts are 5 preferably so proportioned that even when the minimum degree of suction is present in the float bowl 60 a small amount of air is admitted through the orifice |10. It is to be further understood that the degree of suction maintained in the float bowl Bqis always slightly greater than that necessary to overcome the then existing fuel lift head. The metering pin |6`4' is preferably made adjustable. In the form shown a screw driver may be inserted through the opening |18 in the cap |54 w and engaged with teeth |80 suitably provided on an enlargment of the sleeve |68 to rotate the same ,to any desired adjusted position. 'I'he sleever |68 may be locked in the adjusted position by a screw |82. y The primary nozzle 22 must overcome the suction existing in the float bowl 60 in order to draw fuel therefrom. In the normal operation of my carburetor the degree of suction existing in the 0 float bowl is less than the maximum and, therefore, my carburetor operates more efficiently and provides greater .power except under Vthe unusual condition where the fuel in the tankv 66 is low and the automobile is climbing a maximum grade. Under this one unusual condition my carburetor is just as efficient as the fuel lift carburetors heretofore known and under all other conditions it is superior to such carburetors.

While I have illustrated and described only one embodiment of my invention, it is to be understood that my invention is not limited to the precise details shown and described but may assume various forms, and that the scope of my. invention is to be limited solely by the following claims.

I claim:

1. In a fuel lift carburetor of the class described, the combination of a nozzle, a float bowl for supplying fuel thereto, said nozzle having a primary air inlet, a mixing chamber into which said nozzle discharges, a secondary air valve for regulating the supply of secondary air to said mixing chamberfa -booster for creating suction in said float bowl, means controlled by said secondary air valve for regulating the degree of suction produced by said booster, a source of fuel supply for said float bowl located at variable levels with respect to said bowl whereby the head through which the fuel must be lifted varies, mechanism for regulating said secondary air valve in accordance with variations in said head, and means for adjusting said mechanism.

2. 'A fuel lift carburetor for automobiles having a main fuel tank spaced from the carburetor whereby the difference in head between the carburetor and the surface of the fuel in the fuel tank varies, comprising a nozzle, a chamber from which said nozzle is supplied with fuel, a booster 4for creating suction in said chamber, conduit fuel, the upper surface of the fuel in said tank varying in elevation with respect to said iioat `-bowl, means including a diaphragm chamber connecting said tank and float bowl, a diaphragm in said chamber assuming different positions corresponding to different levels, a booster for creating suction in said float bowl, suction operated means for regulating said booster, and suction relieving mechanism for said last mentioned means controlled by said diaphragm.'

4. In a fuel lift carburetor of the class described, y

the combination of a nozzle, a float bowl from whichsaid nozzle is supplied with fuel, a fuel tank from which fuel is sucked to said float bowl, the degree of suction required to draw fuel from the fuel tank to the float bowl beingvariable, suction operated means for creating suction in said float bowl, other suction operated means for regulating said first mentioned suction operated means, and a third suction operated means for regulating said second suction operated means pursuant to said variable requirements.

5. In a fuel lift carburetor of the class described, thecombination of a nozzle, a iioat bowl for supplying fuel thereto, a fuel tank from whichA phragm chamber interposed between said float bowl and said tank, a diaphragm in said chamber having one surface exposed to the fuel passing 4of suction existingtherein, a source of fuel for from said tank to said float bowl, a spring for urging said diaphragm in a direction to enlarge said chamber, a pin movable with said diaphragm,

va by-pass variably controlled by said pin, and

means regulated by said by-pass for varying the degree of suction obtaining in said float bowl.

6. In a fuel lift carburetor of the class described, the combination of a nozzle, a float bowl for supplying fuel thereto, said nozzle having a primary air inlet, a mixing chamber into which said nozzle discharges, a secondary air Valve for regulating the supply of secondary air to said mixing chamber, a variable chamber beneath said secondary air valve, means for admitting suction to said chamber, a spring for expanding said chamberin opposition to'said suction, a booster for creating suction in said float bowl, a pin movable with said air valve to regulate 'the degree tof suction produced by said booster, means for admitting air to said variable chamber to reduce the degree said bowl variable in elevation with respect thereto, and mechanism responsive to said variations in elevation for regulating said air admitting means.

7. In afuel lift carburetor of the class described, the combination of a nozzle, a float bowl constituting a source of fuel supply for said nozzle, a

main tank from which said float bowl is supplied with fuel by suction existing in said float bowl, the degree of suction required to draw fuel from said main tank to said float bowl being variable with differences in head between said float bowl and the top of the fuel in said main tank, a booster for creating suction in said float bowl, and means controlled by said variation in head for regulating the suction created in said float bowl by said booster.

8. In a fuel lift carburetor of the class described,

the combination of a nozzle, a float bowl from which said nozzle is supplied with fuel, a oat controlling the admission of fuel to said oat bowl, a main tank constituting a source of fuel supply for said float bowl, the head between said float bowl and the top of the fuel in said tank being variable, means for creating suction vin said float bowl, and means independent of said oat for varying the suction in said float bowl in accordance with said variations in head.

9. In a fuel lift carburetor of the class described, the combination of a nozzle, a oat bowl from which said nozzle is supplied with fuel, said nozzle having a primary air inlet, a mixing chamber into which said nozzle discharges, a secondary air Valve for regulating the supply of secondary air to said mixing chamber, a booster for creating suction in said float bowl, means controlled* by said secondary air valve for regulating said booster independently of said nozzle, a fuel supply for said float bowl located at variable distances below said float bowl, and means for automatically controlling said secondary air valve in accordance with said variable distances.

10. In a fuel lift carburetor of the class described, the combination of a fuel chamber, an inlet conduitfor said fuel chamber, said conduit connecting said fuel chamber with a fuel supply capable Aof varying its height with relation to that of said chamber,A means for creating suction in said fuel chamber to draw fuel thereinto from saidfuel supply, means for maintaining the fuel in said fuel chamber between given levels, and means indpendent of the level of fuel in said fuel chamber for automatically regulating said suction to conform at any given time to the difference in height between said fuel chamber and said fuel supply.

ROBERT F. BRACKE. 

